SAW devices are preferred over widely used transmission line components because acoustic waves have a substantially shorter wave length at their operating frequency than those of electromagnetic waves which travel at the speed of light. Therefore, for a given operating frequency, a SAW resonator filter provides a smaller sized structure than a transmission line, making them suitable for miniaturized radio frequency applications. For the above reasons, the popularity of SAW structures in radio frequency applications, especially in resonator filter applications has been steadily increasing.
A lot of effort is being exerted in the field of SAW devices in developing higher coupling coefficient materials for the use in SAW devices. The higher coupling materials can be utilized in designing SAW devices having higher performance specifications. In particular, SAW resonators can be designed having wider bandwidth and lower insertion loss in smaller sizes, as higher coupling coefficient materials are developed. A need thus exists for a SAW device which can provide for increased coupling while using the same piezoelectric material.